The reference you give, among other things, says: "rdfs:Datatype is
both an instance of and a subclass of rdfs:Class. Each instance of
rdfs:Datatype is a subclass of rdfs:Literal."
So the build in datatypes such as xsd:int, by this definition, would
be a subclass of rdfs:Literal. However, according to [1] (OWL 1.0)
Definition: An OWL vocabulary V consists of a set of literals VL and
seven sets of URI references, VC, VD, VI, VDP, VIP, VAP, and VO. In
any vocabulary VC and VD are disjoint and VDP, VIP, VAP, and VOP are
pairwise disjoint. VC, the class names of a vocabulary, contains
owl:Thing and owl:Nothing. VD, the datatype names of a vocabulary,
contains the URI references for the built-in OWL datatypes and
rdfs:Literal.
If I understand this correctly, it says that VC (the class names of
a vocabulary) and VD(the datatype names of a vocabulary) are
disjoint. That is, a datatype is not a class. Only classes have
instances. So even for the built-in xsd:int, the statement from RDFS
"xsd:int, is a subclass of rdfs:Literal" can't hold. And so user
defined datatypes are no different than the builtins.
Does that look the appropriate answer to your question?
-Alan
[1] http://www.w3.org/TR/owl-semantics/direct.html#3.1
On Dec 6, 2006, at 7:48 PM, Holger Knublauch wrote:
>
> Thanks, Jeff. But in RDF Schema, the pre-defined system datatypes
> such as xsd:int are instances of rdfs:Datatype as well [1]. Are
> user-defined datatypes different from system datatypes, or is OWL
> 1.1 changing the RDF Schema semantics here? Apologies if this has
> been discussed and written down elsewhere - any pointers are
> appreciated.
>
> Regards,
> Holger
>
> [1] http://www.w3.org/TR/rdf-schema/#ch_datatype
>
>